What Is the MMP-9 Test?

If you've been told you could benefit from having a matrix metalloproteinase-9 (MMP-9) test for your dry eye, you may wonder exactly what that means for you. MMP-9 is an enzyme that has been linked to signs of inflammation on the surface of the eye that may be causing you discomfort.

A test can check levels of MMP-9 enzyme if your eye doctor (ophthalmologist or optometrist) suspects you have dry eye or is trying to determine how to best treat it. The test can be given in the office where you are being evaluated for your dry eye in just a few minutes.

This article will discuss the MMP-9 test, how it works, its uses, its benefits, risks, and its Food and Drug Administration (FDA) status.

How It Works

The test looks for the MMP-9 enzyme in a small sample of tears. It is a single-use, disposable test.

A wand with soft fleece on the end will be dabbed along the inside of your lower eyelid. The healthcare provider will stop between every few dabs to allow you to blink. Only six to eight dabs are needed.

After enough sample tears are collected, the wand is placed into a test cassette. The results are read by the healthcare provider after 10 minutes.

The appearance of a control line indicates the test has been done right. If a test line appears, the test result is positive. This means MMP-9 levels are high enough to cause underlying inflammation on the eye's surface.

Uses

Many people have dry eye, in which they don't produce enough tears or the tears they make have a composition that is not quite right. Dry eye symptoms such as the following help identify the condition:

• Experiencing a burning or gritty sensation
• Having blurry vision
• Noticing that your red eyes become redder as the day goes on
• Feeling eye discomfort

These symptoms can be subjective. Testing for MMP-9 determines if it is elevated and guides dry eye treatment.

If testing shows that you have elevated MMP-9 levels, indicating you have dry eye-related inflammation, your healthcare provider may recommend anti-inflammatory treatments such as:

• A short course of corticosteroid eye drops (ophthalmic solution)
• Oral Vibramycin (doxycycline)
• Restasis (cyclosporine) eye drops to modulate the immune system near the eye and reduce inflammation in the tear glands
• Xiidra (lifitegrast) eye drops to disrupt the inflammatory reaction that leads to dry eye
• Autologous serum eye drops (the noncellular part of your blood is used to make eye drops)

Benefits

Testing for elevated MMP-9 levels can help ensure your healthcare provider is using a treatment that will get to the root of your dry eye. Other dry eye tests, like tear osmolarity or Schirmer's tear test, may show that your eyes are dry but not aid in determining the possible cause.

The benefits of MMP-9 testing are:

• A prompt dry eye diagnosis
• Determining appropriate treatment at the outset
• Better dry eye management

A positive MMP-9 test means there is inflammation in the area. Still, it doesn't mean inflammation is necessarily from dry eye. The inflammation can be from something mechanical, such as rubbing your lid on the eye's surface. But, the test can still point the way to getting the right diagnosis.

Those who can benefit from knowing they have elevated MMP-9 levels from dry eye include:

• Anyone who is looking to undergo an eye procedure to improve their vision, such as LASIK (laser-assisted in situ keratomileusis) or PRK (photorefractive keratectomy), and needs to know if they have dry eye that should be treated first
• Those who want to undergo cataract surgery with more expensive premium lenses that can allow them to see at different distances (they may not get the surgical results they want because of dry eye they weren't even aware they had)
• Those who have been newly diagnosed with dry eye and need to ensure the treatment is addressing the problem
  

If the MMP-9 test is negative, but your symptoms still point to dry eye, the exam can still be of benefit. Instead of wasting time trying anti-inflammatory medication that won't help here, you can be immediately offered the following treatments:

• Artificial tears: Lubricating eye drops
• Punctal occlusion: A quick procedure in which the opening through which the tears normally drain is temporarily blocked, allowing your tears to collect so that there are more available
  

Risks

On rare occasions, the test may end up with a false-negative result, meaning you have high MMP-9 levels, but the test doesn't show this. A false negative may even happen in severe cases, where levels of MMP-9 are significantly raised. The cause of a false negative may be an inadequate collection of the needed tear samples or an error in transferring the swab to the kit.

A false negative could inadvertently lead to a dry eye treatment delay or akin to what may happen without the test. You may be given treatment that doesn't address eye inflammation.

Legality

The InflammaDry test for MMP-9 received FDA approval in November 2013. It can be used by a healthcare provider's office or laboratory certified to do so. It is not a home test kit.

Summary

Testing for elevated MMP-9 levels can indicate if there is inflammation on the eye's surface causing dry eye. This can be measured with a disposable kit test that can be done in the healthcare provider's office in around 10 minutes.

The kit measures levels of MMP-9 in the tears. Armed with information on MMP-9 levels, your healthcare provider will be able to initiate treatment in order to tamp down on inflammation that may be leading to your dry eyes.

A Word From Verywell

Even when you have all the indicators of dry eye, it may be difficult to determine what's causing it. MMP-9 testing can give you an accurate diagnosis so you can start treatment that can help heal your dry eyes.